1. Field of the Invention
This invention relates to a locking system for a plurality of drawers on a piece of furniture and, more particularly, to structure for preventing simultaneous opening of more than one drawer.
2. Background Art
It is known to provide structure to prevent opening of more than one drawer at a time on a piece of furniture. The purpose of this is to prevent the cabinet from becoming front heavy and tipping as might potentially cause injury to the user. In U.S. Pat. No. 3,404,929, to Wright et al, a cabinet with a plurality of vertically arranged drawers and such a safeguard is disclosed. Each drawer carries a plate which, upon the drawer being opened, deflects a lug on a translatable locking bar to reposition the locking bar so that the locking bar prevents opening of any of the other drawers.
The principal drawback with the Wright et al structure is that it can be defeated by simultaneously opening two drawers. While a user normally would not simultaneously open the drawers, a plurality of drawers may be simultaneously shifted open as during an earthquake. Further, for furniture to meet BIFMA standards, the ability to simultaneously open drawers cannot be present. The Wright et al structure would thus not meet BIFMA standards.
One solution to the above problem is disclosed in U.S. Pat. No. 4,711,505, to Lakso. Lakso utilizes a line of balls in a slotted guide member. An actuator, associated with each drawer, causes a ball to be forced between balls in the slot as an incident of the drawer being opened. The balls are packed sufficiently tightly in the slot that only one ball can be forced between adjacent balls in the line. Resultingly, simultaneous opening of more than one drawer is prohibited.
However, the Lakso structure has numerous drawbacks. First, the actuators have to be separately, manually repositioned by a user in both assembling and removing the drawers. That is, as one drawer is put in place and closed, the actuator associated with the next drawer must be manually set to allow entry of the next drawer into its receptive opening and proper engagement between the next drawer and actuator. If any drawer is assembled with the actuator improperly positioned, damage to the drawer and/or actuator could occur.
The balls and the member defining the slot must be dimensioned to very close tolerances for the structure to operate properly in Lakso. The Lakso structure is thus very dirt sensitive. In the event of any foreign matter finding its way into the slot, the Lakso structure could malfunction. Additionally, even slight distortion of the member defining the ball retention slot could result in malfunction.
The Lakso structure also requires the inventorying and assembly of numerous parts. In the described embodiment, the balls are small and difficult to handle, which complicates assembly, resulting in significant manufacturing costs which must be passed on to the consumer.
Because of the relatively large size of the member in Lakso defining the ball retention slot, a substantial amount of the cabinet must be cut out to recess that member.
The Lakso structure is also very sensitive to drawer movement. That is, if one of the drawers is slightly ajar, the remainder of the drawers may be blocked from opening. This is particularly a problem if the cabinet for the drawers is placed on a non-level supporting surface.
Another problem with the Lakso structure is that there is a limited amount of adjustment possible for the mechanism. Each actuator is adjustable vertical only in increments equal to the diameter of the balls. Fine adjustments to the actuator cannot be made without readjusting the entire member defining the ball receiving slot, which member is intended to be permanently mounted. Alternatively, the pin on the drawer can be relocated, however the drawer is usually made from relatively thin stock, which makes such adjustment difficult and undesirable due to stripping out of the screws.